Such actuators have long been known, see for example U.S. Pat. No. 3,964,457 or U.S. Pat. Nos. 4,313,408 and 4,419,973. A specific embodiment of such an actuator drive, such as for example the duplex-winding rotary ,actuator, is described in British Patent 1,602,507. Idling control systems with a further actuator in a bypass channel, carrying auxiliary air, to the throttle flap for internal combustion engines are described, for example, in published British patent application 2,007,878 or U.S. Pat. No. 4,356,802. In such electromechanical actuators having a continuous characteristic, soiling or the formation of ice can, however, cause an increased hysteresis or else a jamming of the actuator to occur. So, in the past, designs for such actuators were devised which, in the case of a de-energized servo motor or in the case of a failure of the servo motor, moved the actuator with the aid of a spring into a defined throttling cross section which sufficed to supply the internal combustion engine with a quantity of air sufficient for the particular situation. Such a configuration is described in U.S. Pat. No. 4,494,517.